The iPhone 5s was a successful product for Apple in several ways. Apple’s CEO Tim Cook said, “This is our best iPhone launch yet―more than nine million new iPhones sold―a new record for first weekend sales.” A CNet review entitled “Same look, small screen, big potential” touts the device’s “next-gen CPU and motion-tracking chip.”
Recently IAT covered the M7 co-processor, which has the capacity to make activity tracking simpler and more battery efficient. However, several users are reporting accelerometer inaccuracies with the new iPhone 5s, which features the advanced M7 chip, and replicating these inaccuracies with device in Apple Stores. In the image above, the user was able to demonstrate 3 and 4 degrees of variation between iPhone 5 and iPhone 5s devices. A single degree of variance would be tolerable. Other users reported as much as 6 degrees of variation—a staggering and significant difference. And similarly, some users are reporting higher accuracy in previous iPhone versions than the 5s. This shows that several users have inaccurate iPhone 5s devices. This is troubling on many levels.
With the iPhone 5s, Apple changed producers for its accelerometer component. According to teardowns by iFixit and EDN, the iPhone 5 used the LIS331DLH 3-axis accelerometer and the L3G4200DH gyroscope, which are both made by STMicroelectronics. According to a Chipworks teardown, the iPhone 5s (see the M7 teardown) uses a gyroscope component from STMicroelectronics, but Apple switched to Bosch Sensortec for the accelerometer, using the BMA220 3-axis accelerometer. According to the companies’ websites, the old accelerometer was capable of higher data output than the new accelerometer (16 bit output compared to 6 bit digital resolution). The Bosch accelerometer also has more typical output noise and a higher Zero-g Offset than the STMicroelectronics component–two aspects also contributing to the lower level of accuracy in the iPhone 5s. This new accelerometer might be a source of users’ issues measuring levels.
For a company making such a large splash in wearables and making so much of the M7 and its capabilities to drive the wearable revolution by putting the phone at the center of much of it, we are left wondering not only why this is happening, but how quickly Apple will respond and resolve this issue. After all, powerful accelerometers with greater resolutions are crucial if developers are to be enabled to build more useful and accurate activity tracking apps around Apple.